The present invention relates to a shape memory organic material and a preparation method thereof, especially to an organic polyurethane shape memory material and a preparation method thereof that are applied to materials with shape recovery property.
Smart material is a novel functional function that senses external stimuli. Self-judges and take actions and such material has been studied extensively with great application potential. They may be used in daily lives, information technology and even national defense industry. Generally, smart materials have following features:
(1) sensitivity: sensitive to strength and change of environmental stimuli such as load, stress, strain, vibration, light, heat, electricity, magnetism, chemical or nuclear radiation.
(2) response ability: according to environmental and internal changes, dynamically have a response.
(3) self-adjustment and repair: repair partial damages or destruction through adaptive or regeneration mechanism.
The most common smart material is shape-memory material that is divided into three categories.
(1) Metal Alloy:
In 1963, Buechler etc. described Shape-memory feature of the nickel-titanium alloy by phase transition of materials under different temperature. Due to its biocompatibility, such material is extensively applied to surgery device and implant.
(2) Ceramic:
Wei etc. disclosed ceramic material such as ZrO2. Like metal alloy, the ceramic material is applied with temperature variations or stress so as to make material structure phase transition occur.
(3) Polymer:
There are classified into two types chemical cross-linking and physical cross-linking. Earlier in 1960, Polyethylene (PE) molecules are joined by covalent cross-linking so as to be heat shrink tubing for covering wires. The deformation is triggered by melting temperature of the PE while covalent cross-linking fixes the deformation. As to poly(vinyl chloride) (PVC), high cross-linking is obtained by heating and the material is also shape-memory material. In physical cross-linking system such as gel, the volume and swelling of polymer are changed by PH vale, dissolvent and sensitivity to ionic strength. But it's main shortcoming is poor mechanical strength.
However, metal and ceramic material both have disadvantages of high cost, poor processability and difficulty in modification. As to the polymer gel system, the mechanical strength is poor. Thus there is a need to provide a new organic polyurethane shape memory material that has advantages of low cost, good processability and easy modification. Moreover, the mechanical strength is also improved.